Electro-optic relaxation methods are being used to study the motions of DNA macromolecules in solution. An electric pulse orients the macromolecules and a light beam-photodetector system produces transient signals which are analyzed with a versatile on-line dedicated minicomputer. The computer and specially developed new programs are used to analyze the amplitudes and the time dependence signals (which may be birefringence, dichroism, or fluorescence) and to fit them to mathematical functions for further interpretation in terms of models and mathematical theories. Calf thymus and bacteriophage and plasmid DNA'S are being studied, including superhelical forms. The effects of various binding agents - mutagens, carcinogens, and antitumor drugs - on DNA structure and flexibility are being determined. The objective is to find out how these substances interact with DNA and influence genetic processes.